Food warming apparatus and method

ABSTRACT

In general, one embodiment of the invention is directed to apparatus for warming pre-cooked sandwich buns and the like to a desired holding temperature and then holding the buns at such holding temperature. The apparatus comprises a cabinet having at least one compartment with a bottom wall, a top wall and opposite side walls. Adjacent the bottom of the compartment is at least one heat source for delivering heat to buns in the compartment. A control mechanism controls the heat source to deliver heat to the buns to warm the buns to the desired holding temperature and then to vary the amount of heat delivered to the buns to hold the buns at the desired holding temperature. A related method is also disclosed.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of pending U.S. applicationSer. No. 10/680,626, filed Oct. 7, 2003, titled FOOD WARMING APPARATUSAND METHOD, which is a continuation-in-part of pending U.S. applicationSer. No. 10/611,295, filed Jul. 1, 2003, titled WARMING APPARATUS ANDMETHOD, which claims the benefit of U.S. Provisional Application No.60/394,841, filed Jul. 10, 2002, titled HOLDING OR COOKING OVEN. All ofthese applications are incorporated herein in their entireties for allpurposes.

BACKGROUND OF THE INVENTION

This invention relates generally to food service equipment and moreparticularly to equipment for maintaining previously cooked food attemperatures suitable for serving the food.

In one embodiment, this invention is especially directed to food serviceequipment that is used to heat pre-cooked bread products, such assandwich buns (e.g., hamburger buns), to a desired holding temperatureand then to maintain such products at such temperature before serving.In this regard, it is desirable to have warm buns at the point ofsandwich assembly. A warm bun contributes to the perception of a hot,fresh sandwich.

There are two conventional processes used in the food service industryto warm sandwich buns. The first is to place the buns in a drawerwarmer, which operates at a set temperature and may have humidity addedto keep the buns from drying out. The problem with this method is thatthe temperature remains constant throughout the entire holding process.If the temperature is relatively high to heat the buns rapidly, the bunsmay heat up to a temperature which exceeds the ideal holdingtemperature, causing the bun quality to deteriorate prematurely. If thetemperature is lower, the buns may take too long to reach the idealholding temperature. The second conventional process is to place thebuns in a toaster, which toasts the inside surface of the bun butcontributes very little to raising the temperature of the bun.

There is a need, therefore, for apparatus which can be used in the foodservice industry to heat previously cooked food (such as sandwich buns)relatively rapidly to a desired holding temperature, and then to reducethe heat to the food to maintain the food at that temperature.

SUMMARY OF THE INVENTION

Among the several objects of this invention will be noted the provisionof food warming apparatus which is adapted for heating pre-cooked foodsuch as sandwich buns to a desired holding temperature and for thenmaintaining the food at such temperature in a way which extends thedesired quality of the product; the provision of such apparatus which iscompact and relatively inexpensive; the provision of an improved methodfor rapidly warming bread products such as sandwich buns and thenmaintaining such products at a desired temperature; and the provision ofsuch apparatus and method for maintaining sandwich buns and the like inan environment where the quality of the buns is maintained at a highlevel for a longer period of time.

In general, one embodiment of the invention is directed to apparatus forwarming pre-cooked sandwich buns and the like to a desired holdingtemperature and then holding the buns at such holding temperature. Theapparatus includes a cabinet having at least one compartment. Thecompartment has a bottom wall, a top wall and opposite side walls.Adjacent the bottom of the compartment is at least one heat source fordelivering heat to buns in the compartment. A control mechanism controlsthe heat source to deliver heat to the buns to warm the buns to thedesired holding temperature and then to vary the amount of heatdelivered to the buns to hold the buns at the desired holdingtemperature.

The present invention is also directed to a bun warmer for warmingpre-cooked sandwich buns and the like to a desired holding temperatureand then holding the buns at such holding temperature. The bun warmerincludes a cabinet having a plurality of bun-holding compartments and aplurality of bun-holding pans in the compartments, one pan percompartment. A plurality of covers cover the pans in the compartments toinhibit the escape of moisture from the pans. Each compartment has abottom wall, a top wall and opposite side walls. Adjacent the bottomwall of each compartment is at least one heat source comprising aheating plate and an electric heater for heating the heating plate todeliver heat to buns in the compartment. A control mechanism controlseach heat source independent of the other heat sources to deliver heatto the buns in the compartments to warm the buns to a respective desiredholding temperature for each compartment and then to vary the amount ofheat delivered to the buns to hold the buns at the desired holdingtemperature.

The present invention is also directed to a method of warming sandwichbuns comprising placing the buns in a compartment of bun warmingapparatus for a duration of heating time and heating the buns in thecompartment by delivering heat to the buns. The heating step comprisesvarying the amount of heat delivered to the buns to warm the buns to adesired holding temperature and then to maintain the buns at the desiredholding temperature. The method also includes inhibiting the escape ofmoisture from the buns during the heating step.

Other objects and features will be in part apparent and in part pointedout hereinafter.

BREIF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective of one embodiment of an oven of the presentinvention for warming buns and the like;

FIG. 2 is a top plan of the oven of FIG. 1;

FIG. 3 is a front elevation of the oven of FIG. 1;

FIG. 4 is a right side elevation of the oven of FIG. 1;

FIG. 5 is a vertical section taken on line 5-5 of FIG. 3;

FIG. 6 is a vertical section taken on line 6-6 of FIG. 4;

FIG. 7 is a diagram of a time vs. temperature curve illustrating onemode of operation of the oven of FIG. 1;

FIG. 8 is a time vs. heat source activation curve for the mode ofoperation depicted in FIG. 7;

FIG. 9A is a diagram of a time vs. temperature curve illustratinganother mode of operation of the oven in FIG. 1; and

FIG. 9B is a time vs. heat energy curve for the mode of operationdepicted in FIG. 9A.

Corresponding parts are designated by corresponding reference numbersthroughout the drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIGS. 1-6 illustrate one embodiment of apparatus of the presentinvention, generally designated 1. In this embodiment, the apparatus isa bun warming device (hereinafter referred to as an “oven”) comprising acabinet having an interior, generally indicated at 5, comprising one ormore compartments, each designated 7, for removably receiving quantitiesof food. As shown, the oven 1 has two compartments 7, but is to beunderstood that the number of compartments may be any number more thantwo or less than two.

In the embodiment shown in FIGS. 1-6, the holding oven 1 has a top 9(FIG. 2), a bottom 11, opposite sides 13 and 15 (FIG. 4), an open frontand an open back. A vertical partition 17 separates the interior 5 ofthe oven 1 into two separate compartments 7, each having a bottom wall19, a top wall 21, and opposite side walls 23. The front and back ofeach compartment 7 are open to permit food to be placed into thecompartment and removed from the compartment from both directions (frontand rear). Alternatively, the front and/or back could be closed by oneor more doors or a fixed wall structure.

A heat source 25 is provided in each compartment 7 for delivering heatto the food (e.g., buns or other breads) in the compartment. In theembodiment shown in FIGS. 1, 5 and 6, the heat source, generallyindicated at 25, comprises a metal plate 26 recessed into the bottomwall 19 of each compartment 7, and a suitable heater for heating theplate, such as one or more electrical resistance heating elements (notshown) below the plate. The side and top walls 23, 21 of the compartment7 of this embodiment are not heated. The power delivered by each heatsource 25 ranges from between about 20 and 2,000 watts, desirablybetween about 25 and 1500 watts, preferably between about 30 and 1000watts, more preferably between about 35 and 750 watts and even morepreferably between about 40 and 600 watts. In one embodiment, each heatsource 25 delivers about 600 watts of radiant heat. Reference may bemade to co-assigned U.S. Pat. Nos. 6,175,099, 6,262,394 and 6,541,739,incorporated herein by reference, for further details relating to theconstruction of certain types of heating elements suitable for use inthe heat sources 25. Different heating mechanisms can be used withoutdeparting from the scope of this invention.

In one embodiment, the food placed in the oven 1 is held by one or morepans, generally indicated at 27, each of which has a bottom wall 29, oneor more side walls 31 (FIG. 5) and/or end walls 33, and a top 35 whichmay be open or closed by a suitable cover (to be described later). Thepans 27 can be of any size and any shape but are typically relativelylarge if buns are being held. For example, a common pan shape for bunsis rectangular and commons sizes would include one-third size, one-halfsize and full-size steam table pans. (A one-third size rectangular steamtable pan has a width of about 6- 15/16 in. and a length of about 12-¾in.; a one-half size rectangular steam table pan has a width of about10- 7/16 in. and a length of about 12-¾ in.; and a conventionalfull-size rectangular steam table pan has a width of about 12-¾ in. anda length of about 20-⅞ in.) The depths of the pans 27 typically rangefrom 2.5 in. deep to 8.0 in. deep. Thus, one or more of the compartments7 of the oven 1 may be sized to receive a one-third size pan, one pan 27per compartment, in which case each such compartment should have a widthgreater than 6- 15/16 in. (e.g., about 8 in. or more) and a lengthgreater than 12-¾ in. (e.g., about 13.5 or more). Alternatively, one ormore compartments 7 may be sized to receive a single one-half size pan,in which case each such compartment should have a width greater than 10-7/16 in. (e.g., about 12 in. or more) and a length greater than 12-¾ in.(e.g., about 13.5 or more). Alternatively, one or more compartments 7may be sized to receive a single full-size pan, in which case each suchcompartment should have a width greater than 12-¾ in. (e.g., about 13.5in. or more) and a length greater than 20-⅞ in. (e.g., about 22 in. ormore). Custom pan sizes can be used to accommodate special batch sizesof food product. The compartments 7 of the oven 1 may be sized so thateach compartment can receive only one pan 27 or multiple pans.

The compartments 7 are preferably constructed to prevent (or at leastsubstantially inhibit) the transfer of food flavor from one compartmentto another, as when warming different food products such as onion-toppedsandwich buns and regular buns. (For additional detail regardingpossible constructions to achieve this flavor transfer preventionfeature, reference can be made to the aforementioned U.S. Pat. Nos.6,175,099, 6,262,394 and 6,541,739.)

When placed in the oven 1, a pan 27 is preferably placed directly on theheating plate 26 in the respective compartment 7 for transfer of heat tothe pan. However, it is contemplated that the pan 27 could be placed ona shelf or other support spaced above the heating plate 26.

In one embodiment, a cover, generally indicated at 37, is mounted ineach compartment 7 in a position for overlying the open top 35 of a pan27 placed into the compartment on the heating plate 26. The cover 37includes a flat horizontal panel 39 supported over the pan 27 by pins 41affixed to the side walls 23 of the compartment 7 and received inopenings (e.g., vertical slots) in flanges 43 along opposite side edgesof the panel 39, the arrangement being such that the cover 37 can“float” vertically in the compartment to accommodate pans 27 ofdifferent heights. The panel 39 has upturned lips 45 along its front andback edges for guiding the pan 27 into the compartment 7. The plate maybe a rectangular plate of anodized aluminum sheet. In this particularembodiment, the cover 37 rests on the rim of the pan 27 to hold moisturein the pan to prevent the food therein from drying out. Alternatively,the cover 37 may be mounted at a fixed position spaced above the rim ofthe pan 27 a distance no greater than one inch, more preferably nogreater than about 0.40 inch, and still more preferably no greater thanabout 0.30 in

In the illustrated embodiment, the cover panel 39 is solid and has noopenings in it. However, it is contemplated that the cover 37 may haveone or more openings in it for venting moisture from the pan 27 below.The number, size and pattern of the vent openings will vary depending onthe type of food, holding time, and other factors. Whatever thecircumstances, the number, size and pattern of the opening(s) can beselected to closely control the amount of moisture vented from the pan27 and thus optimize the conditions for maintaining food quality over anextended period of time.

Other cover arrangements are possible. For example, in one embodiment,each pan 27 is covered by a separate removable lid, either with orwithout vent holes for controlling moisture evaporation, therebyeliminating the need for a cover 37 in the compartment 7. In otherembodiments, the pan 27 may be placed in the oven 1 without any lid orcover whatsoever.

The oven 1 includes a control mechanism, generally indicated at 140, forcontrolling operation of the oven 1. Preferably, the control mechanism140 has an operator input device which, in one embodiment, comprises atouch pad 142 which allows the operator to interact with the controlmechanism. The control mechanism 140 may include a separate input devicefor each compartment 7. Alternately, the operator input device caninclude dials, switches and the like known to those in the art. Forexample, rotatably mounted control dials mounted on the cabinet andmovable in a push-and-turn fashion to any user-selected positions canpermit operator input to the control mechanism 140. The controlmechanism 140 may also include associated indicator lights to inform anoperator of the status of a particular compartment 7 or the food withinthe compartment, such as whether the temperature in the compartment isat a desired temperature or whether the food in the compartment 7 isapproaching or has exceeded the desired duration of holding time. Thecontrols may be placed on the front and/or back of the cabinet to allowoperation of the oven 1 from either or both locations. Further operationof the control mechanism 140 is described below.

The control mechanism 140 controls the amount of energy added during thewarming and holding process and can be programmed using suitablesoftware to adjust the energy input throughout the holding process. Inthis regard, it is generally desirable to heat sandwich buns, forexample, relatively rapidly through a danger zone where bacteriamultiply to a desired holding temperature (e.g., 110-150 degrees F. forsandwich buns). As used herein, the term “desired holding temperature”means either a single substantially constant temperature or a range oftemperatures. Once this temperature is reached, it is desirable toreduce the energy input to a level which is sufficient to hold the foodat a safe and optimal serving temperature for an extended period of timewithout losing significant product quality. The control mechanism 140including the aforementioned software is preferably operable to controlthe environment (e.g., temperature) in each compartment 7 of the holdingoven 1 independently of the other compartments 7, although it iscontemplated that the control mechanism could maintain groups ofcompartments or all compartments 7 at the same environmental conditions.

In one embodiment, the control mechanism 140 uses a duty-cycle system tocontrol the heat source 25 in each compartment 7. (As used herein, theterm “duty cycle” means the ratio of heat source on-time to heat sourceon-time plus heat source off-time.) In this system, the controlmechanism 140 comprises a suitable microprocessor and appropriatesoftware to control relays or the like (not shown) that activate theheat sources 25. The control mechanism 140 can be programmed to controlthe heat sources 25 in the compartments 7 to adjust various parameters,such as, for example, the desired temperature of each compartment, therethermalization time, the duration of heated holding time, thepercentage heater on time, and the time base of the duty cycle, as morefully described below. As such, the control mechanism 140 can controloperation of the heat sources independent of one another so that thetemperature in each compartment 7 may be independently controlled.

Typically, the holding oven 1 operates in “heat up and hold” or“rethermalizing” mode. FIGS. 7 and 8 illustrate an example of theoperation of the oven 1 in this mode. In particular, FIG. 7 illustratesa time vs. temperature curve for a complete hold cycle D for onecompartment 7 of the oven 1, and FIG. 8 illustrates a time vs.activation curve for the heat source 25 of that same compartment 7during the hold cycle D. The time vs. temperature curve of FIG. 7 plotsthe temperature of the food product as a function of time. One skilledin the art will understand that this curve can be different for eachtype of food product to be held in the oven 1.

In operation, the control mechanism 140 operates the heat sources 25 toraise the temperature of pre-cooked food (e.g., buns) in eachcompartment 7 to a desired temperature and then to hold the food at thedesired temperature. The process is started by placing a pan 27containing a food product at an initial temperature T, in a compartment7 of the oven 1. (Temperature T, may vary from a frozen or refrigeratedtemperature to ambient or above.) Using the touch pad 142 or other inputdevice, the operator selects a desired holding temperature T (which willbe higher than the initial food temperature T_(I)), and a duration ofholding time D. Alternatively, the control mechanism 140 can beprogrammed so that the operator need only select the type of food to beplaced in the compartment 7, following which the control mechanism 140is pre-programmed to automatically operate the heating source to heatthe pre-cooked food in each compartment 7 according to a predeterminedprotocol suitable for the type of food in the compartment. In eithercase, the control mechanism 140 is operable to activate the heat source25 to raise the temperature of the food product for a duration ofheat-up or rethermalization time, indicated at I in FIG. 7, during whichthe heat source 25 may operate at a high level (e.g., 100% power) untilthe food reaches the holding temperature T at time H. The heat source 25is then deactivated for a time interval indicated at N in FIG. 8,following which the heat source is activated and deactivated during theremainder of the heated holding time C for successive duty cycles G tomaintain the food in the compartment 7 at the desired holdingtemperature T for the duration the total hold time D. In one embodiment,the duration of the heated holding time C includes intervals of the dutycycle G when the heat source 25 is activated as indicated by E andintervals during which the heat source is deactivated, as describedabove.

Set forth below are exemplary control settings for particular foodproducts when the oven 1 is operating in a heat-up and hold mode.

EXAMPLE 1 Hamburger Buns

-   -   Rethermalization time (I)=10 minutes    -   Hold temperature (T)=125° F.    -   Time period without heat (N)=5 minutes    -   Time-base of duty cycle (G)=180 seconds    -   Percent on time (E)=25%    -   Total hold time (D)=45 minutes

In the embodiments described above, the control mechanism 140 uses aduty-cycle system to control the amount of heat delivered to the food bythe heat sources 25. In this type of system, the percentage of heater onand off time is adjusted to vary the energy level as needed to maintainthe food at the suitable holding temperature T. It will be understood,however, that the control mechanism 140 can vary the amount of heatenergy delivered to the food in other ways. For example, the heatsources may be variable-power heaters operable to deliver heat atmultiple discrete energy levels or at an infinite number of levelsbetween full-power and zero power (as by varying the voltage to theheaters), and the control mechanism 140 may operate to increase anddecrease heat delivered by the heaters in a controlled, pre-programmedmanner to maintain a particular food at its ideal holding temperature.

The particular program used by the control mechanism 140 to control aheat source 25 for any given type of food may be determined empirically.Alternatively, the control mechanism 140 can include one or more sensors47 and one or more appropriate feedback loops for each compartment 7 orgroup of compartments of the oven 1. For example, in one embodiment, atleast one sensor 47 is used in each compartment 7 to detect acharacteristic indicative of the temperature of the food in thecompartment 7, and the control mechanism is responsive to signalsreceived from the at least one sensor to control the heat source 25 tovary the radiant heat delivered to the food to maintain it at a holdingtemperature T appropriate for that food. The characteristic detected bythe one or more sensors 47 may be the temperature of the air in thecompartment 7, or the temperature of a surface in the compartment, orthe radiant IR energy emitted by the food in the compartment, or someother characteristic. Thus, the sensor 47 may be a standard temperaturesensor, or an IR emissions detector, or some other type of detectorcapable of detecting the aforesaid characteristic indicative of thetemperature of the food in the compartment 7.

As noted previously, the control mechanism 140 can be programmed fordifferent types of food, so that after food has been placed in aparticular compartment 7, an operator simply selects that type of foodfrom a suitable menu on a display (not shown) on the cabinet. Thecontrol mechanism uses suitable software to automatically select theappropriate predetermined heating protocol for the food selected,including one or more of the following: the ideal holding temperature Tfor the food selected; the duration of warm-up time I and holding time C(“holding duration D”); and the manner in which the heat source 25 ineach compartment 7 is to be varied to maintain the food at the desiredholding temperature (e.g., percent on-time during each duty cycle, ifduty cycles are used). For convenience, the control 140 also includes atimer which times out the holding duration D, and a display 144 whichshows the time remaining until the end of holding duration. The controlmechanism 140 may also include a visual and/or audible alarm foralerting an operator at a predetermined time before the end of theholding duration D, so that steps can be taken to obtain a fresh batchor batches of additional food. (At the end of a holding duration, anyfood remaining in the compartments 7 is typically disposed of andreplaced by freshly cooked food.)

FIGS. 9A and 9B are graphs illustrating exemplary temperature and energyinput during a typical holding cycle of the oven 1. FIG. 9A graphs timev. temperature in one compartment 7. Food introduced into thecompartment 7 at time T₀ warms up to the desired holding temperature attime T₁. Thereafter, the food is substantially maintained at the holdingtemperature for the remainder of the holding duration D. FIG. 9B is agraph of time v. the heat energy delivered by the heat source 25 to thefood. In the particular embodiment shown in this graph, the heat source25 is operated at a first relatively high level (e.g., 100% of maximumpower) during a first phase P1 from time T₀ to time T₁, so that arelatively large amount of radiant energy is delivered to the food. As aresult, the temperature of the food rises relatively rapidly toward thedesired holding temperature. When the temperature of the food reaches(or slightly surpasses) the desired holding temperature, the controlmechanism 140 causes the heat source 25 in the compartment 7 to deliverradiant heat at a second lower level (e.g., 0% of maximum) during asecond phase P2 from time T₁ to time T₂. After the temperature of thefood has equilibrated at the desired holding temperature, which willvary depending on the particular type of food, the control mechanism 140causes the heat source 25 to increase the amount of heat delivered tothe food to a third level (e.g., 25% maximum) sufficient to maintain thefood at the desired holding temperature during a third phase P3 fromtime T2 until the end of the holding period at time T3. The amount ofheat delivered to the food during the third phase P3 is less than duringthe first phase to achieve an optimum holding environment that willextend the holding time without significant loss of product quality.

It will be understood that the graphs shown in FIGS. 9A and 9B can vary,and that the number of phases P1, P2, P3 discussed above can varywithout departing from the scope of this invention. (For example, phaseP2 can be eliminated.)

When introducing elements of the present invention or the preferredembodiment(s) thereof, the articles “a”, “an”, “the” and “said” areintended to mean that there are one or more of the elements. The terms“comprising”, “including” and “having” are intended to be inclusive andmean that there may be additional elements other than the listedelements.

In view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results attained. The oven1 or holding unit described above can be used to rethermalize virtuallyany kind of food products, although it is particularly suited forwarming sandwich buns and the like. The control mechanism 140 of theoven 1 enables an operator to reduce or increase the energy input at anytime during the process, thereby allowing rapid heating of the foodproducts through a temperature zone where bacteria multiply rapidly,followed by a reduction of heat to hold the food at a safe and optimalserving temperature for an extended period during which the quality ofthe food is maintained at a high level. As various changes could be madein the above constructions without departing from the scope of theinvention, it is intended that all matter contained in the abovedescription or shown in the accompanying drawings shall be interpretedas illustrative and not in a limiting sense. For example, while thecabinet shown in the drawing illustrated has having two side-by-sidecompartments 7 arranged in a single horizontal tier of compartments 7,the cabinet could have more than one horizontal tier of compartments,and more than two compartments in each tier. Alternatively, the cabinetcould have multiple compartments 7 stacked one on top of the other in asingle vertical column of compartments.

1. A bun warmer apparatus for warming pre-cooked sandwich buns and thelike to a desired holding temperature and then holding the buns at suchholding temperature, said apparatus comprising: a cabinet having atleast one compartment therein, said compartment having a bottom wall, atop wall and opposite side walls; at least one heat source adjacent thebottom of the at least one compartment for delivering heat to buns inthe compartment; and a control mechanism pre-programmed for controllingthe heat source to deliver heat to the burls to warm the buns to saiddesired holding temperature, and then to vary the amount of heatdelivered to the buns to hold the buns at said desired holdingtemperature.
 2. Apparatus as set forth in claim 1 wherein said heatsource comprises a metal plate adjacent the bottom wall of thecompartment and a heater for heating the metal plate.
 3. Apparatus asset forth in claim 2 wherein the side walls of each compartment are notheated.
 4. Apparatus as set forth in claim 3 wherein the top wall ofeach compartment is not heated.
 5. Apparatus as set forth in claim 1further comprising partitions in the cabinet dividing the cabinet into aplurality of separate holding compartments, each compartment having atleast one heat source therein, and said control mechanism being adaptedfor controlling operation of the heat sources independent of one anotherwhereby the temperature in each compartment may be independentlycontrolled.
 6. Apparatus as set forth in claim 1 wherein said controlmechanism is operable to vary the heat delivered by said at least oneheat source to the buns through a duration of beating time, saidduration comprising a first phase at which heat is delivered to the bunsby the heat source at a first level to warm the buns to said desiredholding temperature, and a second phase at which heat is delivered tothe buns by the beat source at a second level different from said firstlevel to hold the buns at said desired holding temperature.
 7. Apparatusas set forth in claim 6 wherein said control mechanism comprises anoperator input device for selecting a type of bun to be placed in saidcompartment, and software for operating the heat source according to apredetermined protocol depending on the type of bun selected. 8.Apparatus as set forth in claim 7 wherein said control mechanismcomprises an operator display device for counting down a time remainingin said duration of heating time.
 9. Apparatus as set forth in claim 1wherein said control mechanism is programmed to operate said heat sourceaccording to a predetermined protocol to vary said heat delivered tosaid heat source depending on the type of buns placed in thecompartment.
 10. Apparatus as set forth in claim 9 wherein said controlmechanism comprises an operator input device for selecting a type of bunto be placed in said compartment, and software for operating the heatsource according to said predetermined protocol.
 11. Apparatus as setforth in claim 1 wherein said control mechanism comprises at least onesensor in the compartment for detecting a characteristic indicative ofthe temperature of the buns in the compartment, the control mechanismbeing responsive to signals from said sensor to vary the amount of heatdelivered by the heat source.
 12. Apparatus as set forth in claim 11wherein said sensor is a temperature sensor for detecting thetemperature of a surface in the compartment.
 13. Apparatus as set forthin claim 11 wherein said sensor is operable to detect radiant energyemitted by said buns.
 14. Apparatus as set forth in claim 1 wherein saidat least one heat source is operable in successive time-based cycleseach comprising a first on-time interval during which the heat source isactivated and a second off-time interval during which said heat sourceis de-activated, and wherein said control mechanism is operable to varythe amount of heat by changing the ratio of said on-time interval to thesum of said on-time and off-time intervals.
 15. Apparatus as set forthin claim 1 wherein said control mechanism is operable to vary the amountof heat by increasing and decreasing die level of heat delivered by saidat least one heat source without deactivating the heat source. 16.Apparatus as set forth in claim 1 further comprising a cover secured toone or more of said compartment walls for covering a pan in said atleast one compartment to inhibit the escape of moisture from buns in thepan.
 17. Apparatus as set forth in claim 15 wherein said cover floats upand down to accommodate pans having different heights placed in said atleast one compartment.
 18. Apparatus as set forth in claim 1 whereinsaid cabinet has a plurality of compartments arranged side-by-side. 19.Apparatus as set forth in claim 18 wherein said side-by-sidecompartments are sized for receiving one pan per compartment. 20.Apparatus as set forth in claim 19 further comprising one pan in each ofsaid side-by-side compartments.
 21. Apparatus as set forth in claim 1wherein said desired holding temperature is in the range of from about110-150 degrees F.
 22. Apparatus as set forth in claim 1 wherein eachcompartment has a width of 8 inches or greater for receiving a one-thirdsize steam table pan.
 23. A bun warmer apparatus for warming precookedsandwich buns and the like to a desired holding temperature and thenholding the buns at such holding temperature, said apparatus comprising:a cabinet having a plurality of bun-holding compartments therein, eachcompartment having a bottom wall, a top wail and opposite side walls; aplurality of bun-holding pans in the compartments, one pan percompartment; a plurality of covers covering the pans in the compartmentsto inhibit the escape of moisture from the pans; at least one heatsource in each compartment comprising a heating plate adjacent thebottom wall of the compartment and an electric heater for heating theheating plate to deliver heat to buns in the compartment; and a controlmechanism for controlling each heat source independent of the other heatsources to deliver heat to the buns in the compartments to warm the bunsto a respective desired holding temperature for each compartment, andthen to vary the amount of heat delivered to the buns to hold the bunsat said desired holding temperature.
 24. Apparatus as set forth in claim23 wherein said control mechanism comprises an operator input device forselecting a type of bun placed in a respective compartment, and softwareresponsive to said operator input to operate the heat source to heal thebuns in said respective compartment to a pre-programmed desired holdingtemperature, and then to hold the buns at said preprogrammed desiredholding temperature.
 25. Apparatus as set forth in claim 24 wherein saidsoftware is responsive to said operator input device to operate the heatsource to hold the buns at said pre-programmed desired holdingtemperature for a pre-programmed holding duration.
 26. Apparatus as setforth in claim 25 wherein said control mechanism comprises a displayvisible to an operator for counting down the time remaining in saidpre-programmed holding duration.
 27. A method of warming sandwich bunscomprising the steps of: placing the buns in a compartment of bunwarning apparatus for a duration of heating time, and heating the bunsin the compartment by delivering heat to the buns; said heating stepcomprising varying the amount of heat delivered to the buns in acontrolled, pre-programmed manner to warm the buns to a desired holdingtemperature and then to maintain the buns at said holding temperature;and inhibiting the escape of moisture from the buns during said heatingstep.
 28. A method as set forth in claim 27 wherein the buns are placedin the compartment at a temperature less than ambient temperature, andsaid heating step comprises delivering heat to the buns until the bunsreach said desired holding temperature, and then varying the amount ofheat delivered to the buns to maintain the buns at said desired holdingtemperature.
 29. A method as set forth in claim 28 further comprisingsensing a characteristic indicative of the temperature of the buns inthe compartment, and varying the amount of heat delivered to the bunsaccording to said sensed characteristic.
 30. A method as set forth inclaim 29 wherein said sensed characteristic is a temperature of asurface in said holding compartment.
 31. A method as set forth in claim29 wherein said sensed characteristic is an amount of radiant energyemitted by said buns.
 32. A method as set forth in claim 27 wherein atleast one heat source is operable in successive time-based cycles eachcomprising a first on-time interval during which the heat source isactivated and a second off-time interval during which said heat sourceis de-activated, and wherein said control mechanism is operable to varythe amount of heat by changing the ratio of said on-time interval to thesum of said on-time and off-time intervals.
 33. A method as set forth inclaim 27 wherein said amount of heat is varied by increasing anddecreasing the level of heat delivered by a source of heat withoutdeactivating the heat source.
 34. A method as set forth in claim 27wherein said inhibiting step comprises placing the buns in a pan andcovering the pan.
 35. A method as set forth in claim 27 wherein thecompartment has a pan cover affixed to one or more walls of thecompartment, and wherein said inhibiting step comprises placing saidbuns in a pan, and placing the pan in the oven in a position in whichthe pan underlies the pan cover.
 36. A method as set forth in claim 27wherein said desired holding temperature is in the range of from about110-150 degrees F.
 37. A method as set forth in claim 27 wherein saidbun warming apparatus comprises multiple compartments, and wherein saidmethod further comprising programming said bun warming apparatus to heatthe buns in each compartment to a desired holding temperature whichvaries depending to the type of bun placed in the compartment.
 38. Amethod as set forth in claim 27 wherein said bun warming apparatuscomprises an operator display, and wherein said method comprisescounting down on said operator display said duration of heating time.